In my prior U.S. Pat. Nos. 3,968,808; 4,026,313; 4,290,244; and 4,437,275 various portable shelters are disclosed. In my U.S. Pat. No. 3,968,808, a generally semi-spherical framework made of elongate struts and hub means is disclosed which is movable between a collapsed, bundled condition in which the struts are closely bunched and in generally parallel relation and an expanded condition of three dimensional form. As disclosed, such structural frameworks are self-supporting by virtue of self-locking action, particularly with relation to the modules thereof. This self-locking action is achieved, within a module, by an asymmetrical disposition of those struts which extend inwardly from the crossed pairs of struts defining the peripheral sides of the module. In addition to this asymmetry to achieve the self-locking action, the necessary and sufficient condition for the capability for collapsing as well as expanding is that the sum of the distances from one of a pair of corresponding hub means along a strut to its pivotal connection with a crossing strut and back along the crossing strut to the other of the hub means is a constant value for all pairs of pivotally crossing or scissored struts connected to each pair of inner and outer hub means.
In the U.S. Pat. No. 3,968,808, domes, cylinders and modules are disclosed and in the dome structures, the framework is based upon a spherical icosahedron as defined by Buckminster Fuller and one face of which is illustrated in FIGS. 25 and 27 of that patent. By causing a zone of sliding connections in the framework, as for example as indicated at 110 in FIG. 1, three forms of maximum, though incomplete, possible triangular packing within an icosahedron face are disclosed in FIGS. 25 and 27. The incomplete triangular packing is self evident in FIG. 25 whereas in FIG. 27, either the crossed pair of struts 344 or the two crossed pairs of struts 340 and 342 are left out in order to attain the expandable/collapsible framework with the aforesaid zone 110 of sliding connections between crossed struts.
In my U.S. Pat. No. 4,026,313, the full triangular packing of each icosahedron face is made possible by providing alternate zones 18 and 20 of sliding and pivoted connections as shown in FIG. 1 of that patent. For a cylindrical framework, the alternate zones are shown at 62 and 64 in FIG. 2. FIGS. 10-12A illustrate rectangular modules of the general type which may be employed in this invention. U.S. Pat. Nos. 4,290,244 and 4,437,275 are divisions of U.S. Pat. No. 4,026,313 and are directed to modules per se and/or to a module or an assembly of modules in the form of a panel thereof, respectively. Modules such as these may be employed in this invention, although as will be pointed out hereinafter, any module format which is capable of expanding to three dimensional form and collapsing into a bundle is usable in this invention.
It will be noted that in all of the dome or cylinder structures as disclosed in the aforesaid patents, although it is possible to achieve full triangulation, it is not possible to achieve pivotal connection between all of the pairs of crossed struts due to the necessity for providing the zone or zones of sliding connections.
In all of the dome or cylinder framework structures of the above prior patents, movement from the collapsed condition to the expanded condition involves expansion of the base of the structure from the bundled condition outwardly toward and finally to the fully expanded position of the base. Conversely, when the structure is collapsed, the base retreats inwardly from the fully expanded position to the bundled condition. Expansion or collapse is effected by pushing upwardly on the center of the structure or pulling downwardly on the center of the structure, respectively.
Thus, expansion and collapse in such frameworks occurs progressively within the framework and, more particularly, either expansion or collapsing commences predominantly at the top interior of the framework and expands outwardly therefrom toward the base of the framework, the base dimension in the expanded condition representing the maximum position to which the base expands or from which it retreats.
In my aforesaid prior patents, as in this invention, the framework is covered with flexible covering material to provide a shelter function.